Help! Repeats in Research?

I am a student in Anatomy Ph.D. program. I would appreciate answers from not only neuroanatomists,
but also scientists from other fields.The question is:
In studying neural topographical connection by neural tracing technique, the tracer needs to be
delivered to the target nucleus at medial, intermediate, or lateral parts, for example. Each
animal receives one injection. If on serial sections all these injections are at the desired
locations, should these experiments be repeated? If the animals used are rodents, there might be
less hesitation to do the repeats. What if the animals used are macaca monkeys? Most of the
neuroanatomical publications do not have repeats for their successful injections. Is individual
variation a major concern in such studies? How should the theoretically possible variation be
addressed? Of course doing repeats would be safe in terms of variation, but would it be safely
considered frugal with the resources in terms of the NIH grant proposal review?
Yonghua Tai
Department of Anatomy
The University of Iowa
ytai at blue.weeg.uiowa.edu